The present invention relates generally to apparatus and methods for removing occluding materials from body lumens. More particularly, the present invention relates to the construction and use of atherectomy catheters with an ability to view atheroma and other materials to be excised from blood vessels.
Cardiovascular disease frequently arises from the accumulation of atheromatous material on the inner walls of vascular lumens, particularly arterial lumens of the coronary and other vasculature, resulting in a condition known as atherosclerosis. Atherosclerosis occurs naturally as a result of aging, but may also be aggravated by factors such as diet, hypertension, heredity, vascular injury, and the like. Atheromatous and other vascular deposits restrict blood flow and can cause ischemia which, in acute cases, can result in myocardial infarction. Atheromatous deposits can have widely varying properties, with some deposits being relatively soft and others being fibrous and/or calcified. In the latter case, the deposits are frequently referred to as plaque.
Atherosclerosis can be treated in a variety of ways, including drugs, bypass surgery, and a variety of catheter-based approaches which rely on intravascular widening or removal of the atheromatous or other material occluding a blood vessel. Of particular interest to the present invention, a variety of methods for cutting or dislodging material and removing such material from the blood vessel have been proposed, generally being referred to as atherectomy procedures. Atherectomy catheters intended to excise material from the blood vessel lumen generally employ a rotatable and/or axially translatable cutting blade which can be advanced into or past the occlusive material in order to cut and separate such material from the blood vessel lumen. In particular, side-cutting atherectomy catheters generally employ a housing having an aperture on one side, a blade which is rotated or translated by the aperture, and a balloon or other deflecting structure to urge the aperture against the material to be removed.
Although atherectomy catheters have proven to be very successful in treating many types of atherosclerosis, existing catheter designs may be further improved to provide enhanced performance. For example, in nibbler-type atherectomy catheters and in material excising devices in general, it would be desirable to view the material to be removed prior to the removal step. Furthermore, it would be advantageous if this imaging capability were provided on the same catheter or device which performed the cutting procedure, thus reducing the amount of surgery time spent exchanging imaging and cutting devices. Although some existing catheters provide imaging capability, these devices generally require repositioning of the catheter and the cutting element between imaging and cutting procedures. This undesirably limits the ability of the surgeon to view the exact area of occlusive material to be removed prior to the cut. Such known devices also typically cause the user to first scan a large, less precise area of body lumen. It would be desirable if the device could image the precise area to be excised immediately preceding the cut. Additionally, the repositioning of the entire catheter between imaging and cutting may cause the cutting element to remove material from a location different than the one that was imaged. This decreases the effectiveness of the cutters and may accidentally damage the body lumen. Known imaging atherectomy catheters also have difficulty imaging through the area of the cutting window during catheter delivery. The sharp edges of the cutter on known atherectomy catheters are typically exposed during imaging and thus prevent simultaneous delivery and imaging by the device, since those exposed edges may accidentally catch and tear into the body lumen. For example, in U.S. Pat. No. 5,634,464, an imaging transducer is mounted on a rotatable cutter. Imaging can be performed either while the cutter is rotated or while it is merely axially translated (without rotation). In either case, the cutting blade is exposed during imaging.
For these reasons, it is desired to provide intravascular catheters which have imaging capability that enables a physician to differentiate between desirable tissue structure and undesirable fatty deposits to be removed from a body lumen. It is desirable that the imaging and cutting of material can occur without having to reposition the catheter between such procedures. It would also be desirable if the atherectomy catheter could interrogate and view the vessel while the cutter is delivered through the body lumen or vasculature. It would still further be desirable to provide atherectomy catheters having imaging capabilities which can be utilized while the blade of the atherectomy device is unexposed to the blood vessel. At least some of these objectives will be met by the catheter and method of the present invention described hereinafter and in the claims.
The present invention provides catheters, kits, and methods for removing material from a body lumen. More particularly, the present invention provides an atherectomy catheter, such as catheters having axially translatable, non-rotating cutting blades, with an imaging capability so that areas of the body lumen can be imaged and evaluated before the cutting procedure.
In a first aspect, the present invention provides a catheter for use in excising material from a body lumen. The catheter comprises a catheter body, a cutting blade, and an imaging device. The cutting blade is mounted on the catheter body and configured to move between a material capture (open) position and a closed position. When the cutting blade is in the closed position, the blade substantially closes an aperture or xe2x80x9ccutting windowxe2x80x9d on the catheter body. The imaging device which is usually mounted on or coupled to the cutting blade is configured to be in an imaging position when the cutting blade substantially closes the aperture or cutter window. This allows the imaging device to survey material within a xe2x80x9ccutting zonexe2x80x9d of the atherectomy catheter, preferably precisely at the location where severing of the material will occur, most preferably being aligned with the location of a cutting edge on the cutting blade when the blade is in the capture configuration. By allowing the imaging device to view materials within this cutting zone, preferably precisely at the spot where severing of the material will occur or be initiated, the material may be imaged and then removed from the body lumen without having to reposition the catheter between each step. Furthermore, by having the cutter blade in a substantially closed position, the sharpened edges of the blade are not exposed to the tissue of the body lumen. This advantageously allows the catheter to image tissue while the catheter is delivered through tortuous vasculature without risk that the sharpened edge of the cutting blade will accidentally penetrate tissue during the delivery process.
In one embodiment, the present invention provides a catheter having a telescoping cutting blade that extends outwardly from an aperture on the catheter body. The cutting blade has a first open position leaving a gap between the blade and the catheter body to define a cutting window. Material targeted for removal will intrude into the cutter window and be sheared off when the telescoping cutting blade is retracted into a second closed position. The cutting window defined by the gap is typically a directional, side-opening cutting window. The material imaging device is typically located at a distal end of the telescoping cutting blade. In this embodiment, the material imaging device can provide information regarding the body lumen when the cutting blade is an open or a closed position.
In another embodiment, a catheter of the present invention comprises a catheter body having a side-opening aperture having a cutting blade for shearing off material that intrudes into the aperture or cutting window. A material imaging device is coupled to the cutting blade so that the imaging device will be in an imaging position when the blade substantially closes the cutting window. The imaging device in this embodiment is located behind the cutting edge of the cutting blade.
In another aspect, the present invention provides a method for removing material from a body lumen. The method comprises positioning a catheter body having a cutting blade adjacent to a target material in the body lumen. The cutting blade has a material imaging device and the blade is mounted on the catheter body to excise material which enters a cutting window defined at least in part by the catheter body. The material is imaged when the cutting blade substantially closes the cutting window. It should be understood of course that the material imaging device could be a variety of sensors such as an ultrasound transducer array or optical fibers for optical coherence tomography. The imaging typically occurs prior to cutting. The cutting blade is then withdrawn to allow material to intrude into the cutting window for cutting and removal.
In a still further aspect, kits according to the present invention will comprise a catheter having a material imaging device. The kits will further include instructions for use setting forth a method as described above. Optionally, the kits will further include packaging suitable for containing the catheter and the instructions for use. Exemplary containers include pouches, trays, boxes, tubes, and the like. The instructions for use may be provided on a separate sheet of paper or other medium. Optionally, the instructions may be printed in whole or in part on the packaging. Usually, at least the catheter will be provided in a sterilized condition. Other kit components, such as a guidewire or material imaging accessories, may also be included.
A further understanding of the nature and advantages of the invention will become apparent by reference to the remaining portions of the specification and drawings.